The overall objective of this project is to obtain an understanding of the regulation and mechanism of action of DR5P aldolase through a combination of biochemical and genetic studies. The main approach to the problem is to do a comparative analysis of the structure of the wild-type enzyme and a number of mutationally altered proteins isolated from DR5P aldolase negative mutants. Specifically, mutants altered in the active site region have been isolated, genetically mapped and are being analyzed for their amino acid change. This will eventually lead to the location of the active site region in the protein and a correlation with the genetic map for this enzyme. Studies on the regulation of this enzyme suggest that it is in a regulon made up of 3 operons under the control of a single primary regulator (deo R product). The role of the nucleoside catabolic enzymes in the regulon in cellular metabolism is also under investigation.